The present invention relates broadly to a casing member for a WDM add/drop multiplexer unit. The present invention also relates to an optical network node and to an optical network.
Optical networks may be classified into long haul optical networks, metro optical networks, access optical networks and enterprise gear-optical networks. Distinctions between the different types may in a first instance be drawn on the basis of physical transmission distances covered, decreasing from long haul optical networks down to enterprise gear-optical networks, with the latter being typically implemented within one location e.g. in one office building.
The different types of optical networks can also be distinguished in terms of the physical environment in which in particular add/drop equipment is located. For example, for enterprise gear-optical networks, the add/drop equipment is typically located inside of air conditioned buildings, and therefore no particular extreme temperature condition compliance is required to implement such optical networks. For long haul and metro optical networks, which typically involve very complex and expensive equipment, add/drop equipment is typically located in telecommunications carriers central offices and points of presence and are subjected to a limited range of temperatures, which is sometimes referred to as requiring the add/drop equipment to be carrier class compliant. This temperature range is typically in the range of xe2x88x925 to 55xc2x0 C. as required for Telcordia NEBS level 3.
However, in access optical networks the add/drop equipment is typically located in an outside plant (OSP) situation, and thus potentially subjected to a wider temperature range than e.g. carrier class compliance requirements.
Currently, the only optical networks that can be implemented in scenarios where the required add/drop equipment is located in an OSP situation are Time Domain Multiplexing (TDM) based networks. So far, WDM based optical networks have not been deemed suitable for implementation in OSP situations, as currently available WDM equipment is not OSP compatible. However, it would be desirable to implement WDM based optical networks in such an environment, to utilise the larger capacity in the optical domain in access optical networks. It would further be desirable if such an implementation could be achieved in a compact design for the hardware involved.
At least preferred embodiments of the present invention seek to provide a casing member for a WDM add/drop multiplexer module, suitable for use in an OSP situation and facilitating a compact hardware design.
In accordance with a first aspect of the present invention there is provided a casing member for a WDM add/drop multiplexer unit, the casing member comprising:
a backplane for interconnection of components of the WDM add/drop multiplexer unit inserted in the casing member, and
at least one heat sink opening formed in a wall of the casing member disposed to, in use, receive a heat sink structure of a component of the WDM add/drop multiplexer unit in a manner such that the heat sink structure is exposed to an ambient around the casing member when the component is mounted in the casing member, for facilitating maintaining a controlled temperature environment inside of the component.
In one embodiment, the heat sink opening is formed in the backwall incorporating the backplane.
A pair of heat sink openings may be formed in a mirrored configuration on either side of the backplane with respect to a centreplane halfway along the width of the casing member.
The casing member may further comprise a first key member arranged, in use, to prevent a component of the WDM add/drop multiplexer unit from contacting the backplane, when said component is inserted with an incorrect orientation, and wherein the first key member is adapted to cooperate with a heat sink structure of said component.
In one embodiment, the casing member further comprises a second key member arranged, in use, to prevent a component of the WDM add/drop multiplexer unit from contacting the backplane, when said component is inserted with a correct orientation in another component""s intended slot, and wherein the second key member is adapted to co-operate with a third key member formed on said component.
Preferably, the casing member further comprises at least one vent opening in one wall of the casing member.
Advantageously, the casing member comprises at least one pair of vent openings, the openings of the pair being formed in opposite walls of the casing member.
In one embodiment, the at least one pair of vent openings is formed in the sidewalls of the housing.
At least one pair of vent openings may be formed in the top and bottom walls of the housing element.
In one embodiment, the housing element is adapted for mounting onto a rack structure.
The housing element may be adapted to be mounted horizontally or vertically.
In one embodiment, the casing member further comprises a heat sink unit mounted onto the casing member and adapted, in use, when components of the WDM add/drop multiplexer unit are inserted in the casing member, to make thermal contact with at least one of the components, for facilitating maintaining a controlled temperature environment inside of said component.
Preferably, the casing member comprises a locking member arranged, in use, to cooperate with a corresponding locking member of one of the components when the component is inserted to maintain the thermal contact.
Advantageously, the locking member is arranged, in use, to co-operate with the corresponding locking member to bias the component when inserted.
The heat sink unit may be arranged in a manner such that, in use, the interconnection to said component is releasable.
The heat sink unit may be incorporated in the backwall incorporating the backplane.
In one embodiment, the heat sink unit is formed on the backplane.
The heat sink unit may comprise a plurality of substantially planar fins disposed substantially parallel to the backwall of the casing member, and mounted by way of at least one longitudinal mounting member expanding substantially perpendicularly from the backwall. Accordingly, convection airflow between the fins is preferably not inhibited in either a horizontal or a vertical mounting position of the casing member.
The casing element may further comprise at least one fan device mounted on the outside of the housing element and disposed in a manner such that, in use when the heat sink structure of the component of the WDM add/drop multiplexer unit extends through the heat sink opening of the housing element, the heat sink structure is subjected to an airflow generated by the fan device.
In one embodiment, the casing member further comprises at least one baffle structure externally mounted or formed on the casing member, and arranged in a manner such that in use when the casing member is mounted vertically into the rack structure, convection airflow from one heat sink structure or heat sink unit is diverted away from other heat sink structures or heat sink units.